METEOROLOGISTS have blamed Britain’s wet summer on the unusual position of the jet stream, a belt of fast-moving air 36,000ft above the earth that controls the movements of bad-weather systems.

During most summers the jet stream lies across the north Atlantic, effectively penning bad weather there and in the Greenland Sea so that only Iceland and Scandinavia are affected by them.

This allows anti-cyclones, the high-pressure weather systems associated with warm, sunny summer weather, to move up from Europe to cover Britain.

This year, however, the jet stream has moved several hundred miles to the south. This has allowed depressions, the low-pressure weather systems that bring storms and heavy rain, to batter Britain.

The Met Office believes it is possible this weather pattern may now remain over Britain throughout this month and next, making the whole summer a washout.

The situation has been made worse by the hot and sunny weather systems lying over much of central and south eastern Europe. These interact with depressions to generate the storms and cloudbursts behind the recent floods.

Why, though, has the jet stream shifted southwards? Scientists are not sure of all the reasons but believe there is a link to a natural phenomenon known as La Niña.

This occurs when cool water surges up from the bottom of the Pacific off Peru. The water cools the air above it, setting off a series of changes in the Earth’s atmospheric circulation.

Other factors appear to be at work too. One of them could be the warming of the Atlantic. Matt Huddleston, principal climate change consultant at the Met Office, said such conditions were one of the effects of climate change.